Process for the preparation of paper stock



Oct. 12, 1943.

E. COWLES PROCESS FOR THE PREPARATION OF PAPER STCK Filed June 9, 1937mumllll '/0 be used/)7 regu/abi@ 6005/5/07@ 24' 7 l j; VENTOR.

r ATTQRNEYS. l

Patented Oct. 12, 1943 PROCESS FOR THE PREPARATION OF PAPER STOCK EdwinCowles, Hopewell, N. J., assigner to '.lheA Cowles Company, Princeton,J., a corporation of New Jersey Application June 9, 1937, Serial No.147,211

3 Claims.

-This invention relates to processes for treating paper making materialsand particularly for treating waste paper for the preparation of brouspulp or stock suitable for use in the manufacture of paper, boardand thelike.

(Cl. 92-20) v This. application isrled as a continuation in v part of mycopending application Serial No; 27,4-

605, led June 20, 1935.

Waste paper used for this purpose is mixed with considerable trash anddirt of. all kinds, and one of the problems in preparing stock fromwaste paper is the elimination of trashand dirt. 'In the usual processesfor preparing such stock the Waste paper is placed in a breaker beaterwith sufficient water to reduce the consistency to approximately 3% to5%. After the waste paper is partially debered, the resulting pulpy massor stock, still containing considerable quantities of trash and dirt, isremoved from the breaker beater and mixed with additional watersuiiicient to reduce the consistency to approximately 1%. This thinnedstock is then led to a settling trough Wherek extraneous trash of highspecific gravity such as metal objects, glass.' sand, etc., are settledout, following which it is led to a screen (still at a consistency ofapproximately 1%) where suspended trash such as strings, rope,Cellophane, etc., are removed. The fibrous stock which passes throughthe screen is then led to a thickener where the consistency is,raisedyto approximately 5%, after which the thickened stock is refined inbeaters or Jordans before being used.

Processes of this type have several disadvantages. They `require a greatdeal of expensive equipment in the form of screens, settling troughs andthickeners, and, since the waste paper is only partially debered in thebreaker beater, there is a considerable loss of good stock in thescreening operation. A considerable amount of undebered material alsopasses through the screens and has to be deiibered subsequently in thebeaters or Jordans.

Essentially, the prior processes have comprised treating the entireb'odyof stock emerging from the breaker beater to remove therefromsuccessively, first, the heavy trash, and second the sus nded orlight,trash and undeiibered material9,eleaving a residue of cleandeiibered material. AAccording to the present process, on the otherhand, clean defiberedmaterial is withdrawn directly from the main bodyof stock, leaving a.l residue consisting of both heavy and .lighttrashand undebered material. The waste paper to be treated. is preparedin any suitable manner, as by a breaker beater, 'and the crude stock isthen submitted to a combined screening and centrifugal action whichseparates clean deflbered material from both light and heavy types oftrashand undefibered material and also exerts a debering and refiningaction on the stock. In order to` obtain efficient action, `theconsistency of the'stock entering the screen should be less than 3%, andif the main body of stock is prepared ata higher consistency, it shouldbe thinned accordingly. The clean deiibered stock which emerges maybeused directly for paper making or, if desired, may be passed to beaters,Jordans or'other rening apparatus for additional refining before beingused.

The residuerejected by the screen is greatly thinned with additionalWater, preferably by mixture with the return water from the thickener,to a consistency preferably as low as .2% to .6%. This residue, whichcontains some deiibered material, some undebered material and trash, is`then treated to separate the useful material including defiberedmaterial and undefibered material from trash. For this purpose, theresidue is led to a separating device adapted to separate light trashand large pieces of heavy trash from useful fibrous material. Anordinaryscreen may be used for this purpose, .although I prefer to use aseparator of a. type hereinafter referred to. The separating action atthis stage need not be complete, for as hereinafter explained, 'anytrash passing through will be recycled and may be removed during a laterpas.-

sage.

The iibrous material andwater separated from the trash may stillvcontain a considerable amount of undesirable small heavy trash such assand and dirt, and accordingly it is led to a settling tank where solidmaterials of high specic gravity are settled out and materials of lowspecific gravity such as tar may be skimmed off. In view of the very lowconsistency of the material entering the tank. an eicient settlingaction is obtained. Material may be withdrawn continuously from thesettling tank and this material is returned to the screen hereinbeforereferred to. Since the material returned from the passing from thescreen may also be recirculatedv along with the said material.

From the foregoing, it Will-be observed that there is a directwithdrawal in the screen `of clean debered material leaving a residueofv light and heavy trash and undebered material. Furthermore there isacontinuous -recycling of the residue with intermediate removal of bothlight and heavy trash. Thus, whereas in prior proc- -esses the trash wasremoved from the main body of stock, in the present process cleanldeibered material is removed from the main body, and

the trash is removed from the relatively small residue remaining afterthe withdrawal of the clean deiibered material. For this reason theapparatus for separating the trash may be less elaborate than in priorprocesses.

A preferred embodiment of the invention is illustrated in theaccompanying drawing in which the figure is a diagrammatic illustrationin the form of a iiow sheet.

Referring tothe drawing, the raw waste paper is introducedto the breakerbeater I to which sufficient water is added to reduce the con- Varatoris not required to effect a perfect separation, for any trash whichfails to separate out is re-cycled and removed later. It should benoted, however, that because of the extremely low consistency of thematerial flowing through the separator, there is very little loss offibrous material. The remaining Water and fibrous stock ow into thesettling tank 24 which may be conveniently arranged underneath theseparator I8. 'I'he overflow from the settling tank, consisting of waterand partially debered stock, is returned to the screen 6, but ispreferably conducted through the pipe 25 to the compartment 26 which maybe conveniently formed as a part of the head box 8, being separatedtherefrom by the dam 21. The compartment 26 is connected to the screen 6by the pipe 28 and pipe 5. It will be observed that with thisarrangement, partially debered stock returned from the settling tankmay, if dei sired, be mixed with good brous stock and then mixed withany desired proportion of new stock,

the rate of flow of the latter being controlled by controlling thespeed/-of the pump 3 and the opening of the valve 29.

, According to the present process in which there is an initialwithdrawal in the screen 6 of clean delbered stock it is possible tosecure an improved quality of deflbered material which is cleaner thanin prior processes in which the trash is withdrawn from the stock.l Itwill also che observed that since only the residue of rejected stock isclarified, much less equipment is rescreen for purposes set forth insaid patent. As

explained in said patent, the action is such as to permit only cleandefibered material to pass through the. screens, for the combination ofthe screening action with the centrifugal action prevents both light andheavy trash as well as unde- 'flbered material 4from passing through thescreens. The deiibered stock from the said screen may be used directlyfor paper making purposes,

or may be conducted to a thickener, preferably via a pipe I leading to ahead box 8 having a dam 9 over which the stock flows into a compartmentI0 from which it flows through the pipe II to a thickener I2 ofconventional construction. The

thickened stock at approximately 4% to l5% consistency is removed fromthe thickener through the pipe I3 and the water lwhich is extractedflows through a pipe I4 into a sump tank I5.

'I'he rejected stock or residue from the screen 6 is forced through thepipes I6 and II to the separator I8, but before reaching the separator,the residue is greatly thinned by the addition of water from the sumptank I5, which is pumped by the pump I9 through the pipes 20 and 2Iwhich are connected with the pipe I1. As previously stated, it ispreferable `,to add suicient water to reduce the consistency of theresidue to from .2% to .6% consistency. The remaining water from thesump tank may be returned to the settling tank 24 through the pipe 24and used to control the consistency therein. In this manner', all of thewaterv from the thickener is returned to the settling tank eitherdirectly through pipe 24' or through the pipe Il and separator I8.

The separator I8 may be of any desired type,

but is preferably made lin accordance with the quired than in theordinary processes where all l of the stock is required to be clarified.Furthermore; since fibrous material, which is rejected in its rstpassage through the screen is continuously re-cycled via the separatorand settling tank and back to the screen, there is practically no lossof useful fibrous material, for any unde,

fibered material which is introduced from the breaker beater isgradually debered during its circulation through the screen and iswithdrawn as debered material.

It will be understood that the invention may be variously modified andembodied within the scope of the subjoined claims.

I claim as my invention:

l. Process for the treatment of waste paper containing both light andheavy trash for the preparation of paper stock, which comprisespartially debering the waste paper to form a pulpy mass, withdrawing amajor portion of said mass directly in the form of substantially cleandefibered material leaving a single residue of relatively small volumecontaining a mixture of partially defibered material, and both lightland heavy trash, removing both light and heavy trash from said residue,and re-cycling the remainder of partially deflbered material for theseparation of additional debered material.

2. Process for the treatment of waste paper* ing a single residue-arelatively small volume containing a mixture of partially deberedmaterial and both light and heavy trash, removing both light and heavytrash from said residue, and re-cycling the remainder of partiallydebered material for the separation of additionalv debered material.

' v EDWIN COWLES.

